<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>

  <style>
    #d1 {
      width: 200px;
      height: 200px;
      border: 1px solid red;
    }




  </style>
</head>
<body>
<div id="d1">边框测试</div>

</body>
</html>